Bitcoin mining rate will slow down ever more in the future.
The 18th millionth bitcoin was mined on October of 2019
The 17th millionth bitcoin was mined on April of 2018
The 16th millionth bitcoin was mined on December of 2017
The 15th millionth bitcoin was mined on November or December of 2015
1 Million bitcoins were mined every 2 years. Over the years, Bitcoin rewards would be sliced in half again which would cause the bitcoin mining rate to slow down into the future. So 1 million bitcoin would be mined in the next 4 years so the timing rate of mining 1M bitcoin would double and it would keep doubling which would make the mining rate very slow. If there were 22 million bitcoins ever existed, It would take like a few centuries or maybe almost a millennium. But we live in a universe that has at least 21 million bitcoin.